The Arabidopsis GAMYB-like genes, MYB33 and MYB65, are MicroRNA-regulated genes that redundantly facilitate anther development
The Arabidopsis GAMYB-like genes, MYB33 and MYB65, are MicroRNA-regulated genes that redundantly facilitate anther development
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DOI：
10.1105/tpc.104.027920
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发表时间：
2005-03-01
期刊：
影响因子：
11.6
通讯作者：
Gubler, F
中科院分区：
文献类型：
--
作者：
Millar, AA;Gubler, F
绝大多数编码R2R3 MYB结构域蛋白的基因的功能仍然未知。拟南芥MYB33和MYB65基因与大麦GAMYB基因序列相似性高。从两个基因中分离出T-DNA插入突变体，myb33 myb65双突变体在花药发育中存在缺陷。在myb33 myb65花药中，绒毡层在花粉母细胞阶段发生肥大，导致花粉发育的减数分裂前败育。然而，myb33 myb65不育性是有条件的，在更高的光照或更低的温度条件下，其育性都增加了。因此，MYB33/MYB65促进了花药的发展，但不是必需的。两个突变体都没有表现出表型，这意味着MYB33和MYB65在功能上是冗余的。与功能冗余一致，MYB33和MYB65的启动子- β -葡萄糖醛酸酶（GUS）融合在花（萼片、花柱、花托、花药花丝和结缔组织中，但在花药本身中不存在）、茎尖和根尖中具有相同的表达模式。相比之下，MYB33:GUS翻译融合在花中仅在幼花药中表达（与雄性不育表型一致），在茎部分生组织和根尖中未见染色。microRNA靶序列存在于MYB基因中，并且在MYB33:GUS融合中突变该序列导致表达模式扩大，在组织中与启动子GUS系中观察到的相似，这意味着microRNA靶序列限制了MYB33的表达。含有突变microRNA靶点的MYB33转化的拟南芥具有显著的多营养发育缺陷，这表明限制MYB33的表达，特别是在茎尖，对植物的正常发育至关重要。
The functions of the vast majority of genes encoding R2R3 MYB domain proteins remain unknown. The closely related MYB33 and MYB65 genes of Arabidopsis thaliana have high sequence similarity to the barley (Hordeurn vulgare) GAMYB gene. T-DNA insertional mutants were isolated for both genes, and a myb33 myb65 double mutant was defective in anther development. In myb33 myb65 anthers, the tapetum undergoes hypertrophy at the pollen mother cell stage, resulting in premeiotic abortion of pollen development. However, myb33 myb65 sterility was conditional, where fertility increased both under higher light or lower temperature conditions. Thus, MYB33/MYB65 facilitate, but are not essential for, anther development. Neither single mutant displayed a phenotype, implying that MYB33 and MYB65 are functionally redundant. Consistent with functional redundancy, promoter-beta-glucuroniclase (GUS) fusions of MYB33 and MYB65 gave identical expression patterns in flowers (sepals, style, receptacle, anther filaments, and connective but not in anthers themselves), shoot apices, and root tips. By contrast, expression of a MYB33:GUS translational fusion in flowers was solely in young anthers (consistent with the male sterile phenotype), and no staining was seen in shoot meristems or root tips. A microRNA target sequence is present in the MYB genes, and mutating this sequence in the MYB33:GUS fusion results in an expanded expression pattern, in tissues similar to that observed in the promoter-GUS lines, implying that the microRNA target sequence is restricting MYB33 expression. Arabidopsis transformed with MYB33 containing the mutated microRNA target had dramatic pleiotrophic developmental defects, suggesting that restricting MYB33 expression, especially in the shoot apices, is essential for proper plant development.